Approximately 4 million Americans said they were currently using prescription drugs for non-medical purposes in a 1999 report.Commonly prescribed pain medications that can become addictive include: codeine, oxycodone, and sleep disorder drugs.Prescription drugs are the most common form of drug abuse among older people.Fastest growing group of new prescription drug abusers are 12- to 17-year-olds and 18- to 25-year-olds.

Source: National Household Survey on Drug Abuse

(CNN) --Rush Limbaugh announced on his radio program Friday that he is addicted to pain medication and that he is checking himself into a treatment center immediately.

"You know I have always tried to be honest with you and open about my life," the conservative commentator said in a statement on his nationally syndicated radio show.

"I need to tell you today that part of what you have heard and read is correct. I am addicted to prescription pain medication."

Law enforcement sources said last week that Limbaugh's name had come up during an investigation into a black market drug ring in Palm Beach County, Florida. The sources said that authorities were looking into the illegal sale of the prescription drugs OxyContin and hydrocodone.

Limbaugh, who has a residence in Palm Beach County, was named by sources as a possible buyer. He was not the focus of the investigation, according to the sources.

The radio talk show host said he first became addicted to painkillers "some years ago," following spinal surgery. However, he added, "the surgery was unsuccessful and I continued to have severe pain in my lower back and also in my neck due to herniated discs. I am still experiencing that pain."

He had tried to break his dependence in the past and has checked himself into medical facilities twice before, he said.

Limbaugh said that he is "not making any excuses" and that he is "no role model."

"I refuse to let anyone think I am doing something great here, when there are people you never hear about, who face long odds and never resort to such escapes. They are the role models," he said.

He would not provide details of his current problem, citing the ongoing investigation.

"At the present time, the authorities are conducting an investigation, and I have been asked to limit my public comments until this investigation is complete."

Sources said the investigation began nine months ago when Wilma Cline, a former housekeeper at Limbaugh's oceanfront Palm Beach mansion, approached authorities.

"I will only say that the stories you have read and heard contain inaccuracies and distortions, which I will clear up when I am free to speak about them," he said.

Limbaugh has not been charged with any crime.

Earlier this month, Limbaugh resigned from his position as football commentator on ESPN after making remarks that critics considered racist.

Limbaugh said he left the show "Sunday NFL Countdown" to protect the network from the uproar caused by his statement that Philadelphia Eagles quarterback Donovan McNabb was overrated because the media wanted to see a black quarterback succeed.

He did not apologize for the comments and does not consider them to be racist remarks, merely an observation of the media's reaction to McNabb's success.

The revelation about Limbaugh's possible addiction to OxyContin appeared the same week he resigned from ESPN. In the statement read by Limbaugh Friday, he did not name the pain medication he said he's addicted to.

Dr. Drew Pinsky, an addiction specialist in Pasadena, California, told CNN that if Limbaugh is addicted to OxyContin, "We're really talking about opiate addiction. The withdrawal is miserable and painful and it takes a long time to recover."

The disease is insidious, Pinksy said.

"It's a progressive disease, and when it progresses, the house of cards falls." Still, he said, "I've seen miracle recoveries."

Limbaugh is one of the most recognized talk show hosts in the nation and also one of the most controversial. In 2001, he signed a nine-year contract with Premiere Radio Networks, which syndicates his show to nearly 600 stations, for a total salary package reported to exceed $200 million.

It is estimated that nearly 20 million people listen to Limbaugh's show daily.

Also in 2001, Limbaugh learned he had a hearing problem. He was diagnosed in May and told his listeners in October that he was almost entirely deaf as a result of an autoimmune inner-ear disease. He said he had lost 100 percent hearing in his left ear and 80 percent in his right ear.

He successfully had a cochlear implant placed in his left ear to restore his hearing. He announced in January 2002 that he could hear his own radio show "for the first time in nearly four months via a medical marvel."

Until then, he relied solely on a TelePrompTer and his staff's assistance to understand his callers.